Glucose 6-Phosphate Dehydrogenase Isoenzyme Patterns and Chromosomes in Primary Liver Tumors of the Rat¹ Free

Glucose 6-phosphate isoenzyme patterns and chromosomes were studied in 25 primary liver tumors of the rat in order to determine whether the isoenzyme pattern and chromosomes change dependently upon neoplastic transformation, and whether certain changes in the isoenzyme patterns correlate with definite chromosomal changes. Tumors were induced in livers of male rats fed 3′-methyl-4-dimethylaminoazobenzene for the first 3 months and then a normal diet.

Out of 19 tumors whose chromosomes were analyzed, ten were eudiploid, one tetraploid, and two mosaics of eudiploid and eutetraploid cells; the remaining six were aneuploid. Although the enzyme activity varied considerably in different tumors, 20 of the 25 tumors exhibited isoenzyme patterns of either the normal male or female type. Loss of some molecular forms of glucose 6-phosphate dehydrogenases was observed in 5 others, including one chromosomally normal tumor. A similar feature was noted in nontumorous portions of livers from two primary tumor-bearing rats.

Both changes in the isoenzyme pattern and chromosomes observed in the tumors appeared to be independent of the initial neoplastic change.